In the technical field of wind turbine generator systems, the drive train between the rotor and the mostly downstream transmission can be designed in various ways. One possibility is to directly flange the rotor to the transmission, so that an interposed rotor shaft is omitted. In the concept of interest here the torque generated by the rotor is transmitted to the transmission of the wind turbine generator system via a distance-covering rotor shaft. In more powerful wind turbine generator systems, rotor shafts are needed, for example, to distribute evenly the weight and wind forces generated in the area of the top of the tower of a wind turbine generator system.
From DE 102 42 707 B3, a generic drive train is known. It is essentially comprised of an input rotor for transforming the wind energy to a torque, which is flanged to a rotor shaft on one side of the top of the tower of the wind turbine generator system. On the opposite side of the top of the tower, the rotor shaft feeds the rotary motion generated by the rotor into a transmission with a downstream generator. By spacing the rotor on the one hand and the transmission together with the generator on the other hand via the rotor shaft, an even distribution of the weight and reactive forces is achieved in the area of the top of the tower. This spacing requires a suitable support for the rotor shaft with respect to the machine carrier, which forms the top of the tower and which is pivotable with respect to the tower of the wind turbine generator system, which is in turn fixed with respect to the ground, in order to control the position of the rotor with respect to the wind direction.
The support of the rotor shaft with respect to the top of the tower is formed here in the form of a two-point support and therefore comprises a fixed bearing close to the rotor and a loose bearing close to the transmission. While no loads of the rotor are transmitted into the transmission due to this two-point bearing of the rotor shaft, the necessary bearing positions require additional components.
According to another embodiment it is suggested that the front rotor shaft bearing be formed directly as a moment bearing arranged on the hub of the rotor, the moment bearing being fixed to the machine carrier. With the use of a jointed or flexible intermediate member, again, no external forces are transmitted into the transmission. However, the construction of a moment bearing on the rotor side is very complex, because relatively large bearings are necessary for this purpose.
In the technical approach disclosed in EP 1 457 673 A1, a three-point bearing is suggested allowing the rotor shaft bearing to be omitted on the transmission side by displacing this bearing point directly into the transmission. A bearing at the transmission input thus takes over the function of this bearing point. The force flows here via the planet carrier and is passed on via the torque support of the transmission to the carrier structure. Again, a fixed bearing is utilized as the rotor shaft bearing on the rotor side, which is formed here as a spherical roller bearing. In practice, a pivoting motion—if slight—of the rotor shaft about the bearing point of the rotor shaft bearing due to the weight and wind forces must be accepted. With relatively short rotor shafts, in particular, this bending effect can grow to such an extent that the tooth position of the gears on the input side of the transmission comes out of the optimal tooth engagement, which causes progressive wear and a degradation of the efficiency.
Moreover, in this approach of the prior art, a suitable linking element is necessary between the rotor shaft and the corresponding hollow shaft on the input side of the transmission. As a suitable linking element, a clamp ring is used for pressing the distal end of the hollow shaft at the input side of the transmission radially to the inside onto the corresponding end of the inserted rotor shaft. Such a clamp ring has a substantial mass which adds to the overall mass of the drive train. However, particularly in the area of the top of the tower of a wind turbine generator system, the apparatus installed there should have a small overall mass.
It is an object of the present invention to create a drive train of a wind turbine generator system which has a small mass, needs a minimal number of bearing points and still always ensures the optimum tooth engagement within the transmission.
The object is achieved on the basis of a drive train according to the preamble of claim 1 in combination with its characterizing features. The subsequent dependent claims define advantageous embodiments of the invention.